1. Field of the Invention
The present invention relates to for example a reproducing device that performs reproduction so as to support an optical disk-shaped recording medium and a method thereof.
2. Description of the Related Art
For example, optical disk-shaped recording media (hereinafter referred to also as optical disks) such as a Blu-ray Disc (registered trademark) having a physical structure formed by laminating two recording layers have already been commercialized.
For favorable recording and reproduction on an optical disk, the laser power of laser light applied to the recording layers needs to be set appropriately.
Then, for example, light transmittance differs in each layer of an optical disk of the above-described two-layer structure. This means that to be exact, an appropriate laser power differs for each layer, and that therefore recording and reproduction should ideally be performed after changing and setting an appropriate laser power for each layer.
Japanese Patent Laid-Open No. 2008-243339 describes the following “recording” on an optical disk having two or more recording layers.
Specifically, the film thickness information of reflective layers of an optical disk produced by a semitransparent film is obtained from prepackaged firmware of an optical disk device or the optical disk storing the film thickness information in advance, and a recording power adjustment coefficient is calculated. Then, using the calculated adjustment coefficient, recording start power of a second layer or a subsequent layer and write-once start power at a write-once time are set as recording power.
However, in actuality, recording and reproduction on an optical disk of a two-layer structure in the past has been performed as follows without changing laser power.
As one example, for a recording layer on a surface side (outer layer side) of two layers, a limitation within a certain range is imposed on for example a material forming the layer, semi-reflective film characteristics and the like by specifications. That is, by manufacturing the optical disk with the above-described characteristics confined within the range of the specifications, the light transmittance of the recording layer on the outer layer side is secured to such a degree that no problem occurs even when recording and reproduction are performed on the outer layer side and the inner layer side with a same laser power.
As another example, a method is known in which recording and reproduction are performed after recording (formatting) the entire region of the recording layer on the outer layer side. A recording layer in a recorded state has a higher light transmittance than a recording layer in an unrecorded state. Accordingly, a high light transmittance is secured by first setting the entire region on the outer layer side in the recorded state, and thereafter recording and reproduction are performed on the inner layer side with a same laser power.